Predetermined Chirality in Mono- and Dinuclear Cyclometalated Rhodium(III) Complexes

✍ Scribed by Liana Ghizdavu; Brunhilde Kolp; Alex von Zelewsky; Helen Stoeckli-Evans

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 925 KB
• Volume: 1999
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/(sici)1099-0682(199908)1999:8<1271::aid-ejic1271>3.0.co;2-p

✦ Synopsis

Dinuclear and polynuclear metal complexes with octahedral eluent contains NaCl. Modeling the ΛΛ and the ∆Λ isomers of the dinuclear species shows crowding of the pinene centers coordinated to di-or polydentate ligands are often obtained as complicated mixtures of various stereoisomers. groups in both cases; however, the strain can be released by relatively small distortions only in the case of the ΛΛ isomer. Stereospecific synthesis of such species is therefore of high current interest. Chiral derivatives of pyridine can be used NO 3 -cleaves the dichloro bridge, yielding the mononuclear species ∆[Rh(L 2 ) 2 (NO 3 )] (2) in a completely stereoselective for this purpose. Dinuclear µ-chloro-bridged Rh III complexes with two didentate, cyclometalated thienylpyridine-type manner when NaCl is replaced by KNO 3 in the eluent mixture. The molecular structure has been determined by X-ligands at each metal center are formed stereoselectively when pinene groups are fused to the pyridine rings. The two ray structure analysis for both the ∆∆ and the mononuclear complex ∆[Rh(L 2 ) 2 (NO 3 )] (2) in order to confirm the octahedral Rh III centers have homochiral configurations, ∆∆ and ΛΛ. The heterochiral diastereomer ∆Λ is not observed. configuration at the metal center. 1 H-NMR, 13 C-NMR and CD spectra were measured and the latter shows that the CD With (8R,10R)-2-(2Ј-thienyl)-4,5-pinenopyridine [Hth4,5-(R,R)ppy] the ∆∆ to ΛΛ ratio is 9:1 when the separation activity is solely due to the chirality at the metal center.